Toán Lớp 8: x.(x-2)= 16; 2 mũ x+3.2 mũ x=144
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Toán Lớp 8: x.(x-2)= 16; 2 mũ x+3.2 mũ x=144
Comments ( 1 )
x = 1 + \sqrt {17} \\
x = 1 – \sqrt {17}
\end{array} \right.\)
a)x\left( {x – 2} \right) = 16\\
\to {x^2} – 2x – 16 = 0\\
\to {x^2} – 2x + 1 = 17\\
\to {\left( {x – 1} \right)^2} = 17\\
\to \left| {x – 1} \right| = \sqrt {17} \\
\to \left[ \begin{array}{l}
x – 1 = \sqrt {17} \\
x – 1 = – \sqrt {17}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 1 + \sqrt {17} \\
x = 1 – \sqrt {17}
\end{array} \right.\\
b){2^{x + 3}}{.2^x} = 144\\
\to {2^x}{.2^3}{.2^x} = 144\\
\to {2^{2x}} = \dfrac{{144}}{8}\\
\to {2^{2x}} = 18
\end{array}\)